On 09/13/2012 10:03 AM, Anton Vorontsov wrote:
> This command disables NMI-entry. If NMI source has been previously shared
> with a serial console ("debug port"), this effectively releases the port
> from KDB exclusive use, and makes the console available for normal use.
>
> Of course, NMI can be reenabled, enable_nmi modparam is used for that:
>
> echo 1 > /sys/module/kdb/parameters/enable_nmi
>
> Signed-off-by: Anton Vorontsov <anton.vorontsov@xxxxxxxxxx>
> ---
> kernel/debug/kdb/kdb_main.c | 29 +++++++++++++++++++++++++++++
> 1 file changed, 29 insertions(+)
>
> diff --git a/kernel/debug/kdb/kdb_main.c b/kernel/debug/kdb/kdb_main.c
> index 31df170..9fadff1 100644
> --- a/kernel/debug/kdb/kdb_main.c
> +++ b/kernel/debug/kdb/kdb_main.c
> @@ -21,6 +21,7 @@
> #include <linux/smp.h>
> #include <linux/utsname.h>
> #include <linux/vmalloc.h>
> +#include <linux/atomic.h>
> #include <linux/module.h>
> #include <linux/mm.h>
> #include <linux/init.h>
> @@ -2107,6 +2108,32 @@ static int kdb_dmesg(int argc, const char **argv)
> return 0;
> }
> #endif /* CONFIG_PRINTK */
> +
> +/* Make sure we balance enable/disable calls, must disable first. */
> +static atomic_t kdb_nmi_disabled;
> +
> +static int kdb_disable_nmi(int argc, const char *argv[])
> +{
> + if (atomic_read(&kdb_nmi_disabled))
> + return 0;
> + atomic_set(&kdb_nmi_disabled, 1);
> + kgdb_enable_nmi(0);
> + return 0;
> +}
> +
> +static int kdb_param_enable_nmi(const char *val, const struct kernel_param *kp)
> +{
> + if (!atomic_add_unless(&kdb_nmi_disabled, -1, 0))
> + return -EINVAL;
> + kgdb_enable_nmi(1);
> + return 0;
> +}
> +
> +static const struct kernel_param_ops kdb_param_ops_enable_nmi = {
> + .set = kdb_param_enable_nmi,
> +};
> +module_param_cb(enable_nmi, &kdb_param_ops_enable_nmi, NULL, 0600);
> +
> /*
> * kdb_cpu - This function implements the 'cpu' command.
> * cpu [<cpunum>]
> @@ -2851,6 +2878,8 @@ static void __init kdb_inittab(void)
> kdb_register_repeat("dmesg", kdb_dmesg, "[lines]",
> "Display syslog buffer", 0, KDB_REPEAT_NONE);
> #endif
Based on what I commented in the 01/11 patch, we don't want to register a command if the architecture doesn't actually have it, because it just leads to confusion.
It needs to have an "if"
if (arch_kgdb_ops->enable_nmi) {
> + kdb_register_repeat("disable_nmi", kdb_disable_nmi, "",
> + "Disable NMI entry to KDB", 0, KDB_REPEAT_NONE);
}
> kdb_register_repeat("defcmd", kdb_defcmd, "name \"usage\" \"help\"",
> "Define a set of commands, down to endefcmd", 0, KDB_REPEAT_NONE);
> kdb_register_repeat("kill", kdb_kill, "<-signal> <pid>",
>
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